Vapour generators



July 23, 1963 R. H. P. ROW

VAPOUR GENERATORS Filed Dec. 11, 1961 United States Patent 3,098,469 VAPOUR GENERATERS Ronald Henry Paddon Row, Bexley, Kent, England, assignor to Foster Wheeler Corporation, New York, N.Y., a corporation of New York Filed Dec. 11, 1961, Ser. No. 158,404 1 (Ilaim. (Cl. 122-478) This invention relates to water tube boilers having superheaters heated by convection, and means to vary the amount of heat added in the superheater.

The recirculation of cooled gases for attemperation of the hot gases by means of which the superheater is heated so as to control the temperature at the outlet from the superheater is not at all uncommon. In accordance with the invention, however, while cooled gases are recirculated for control of the superheat temperature, they are used not for attemperation of the hot gases but for diverting a variable proportion of the inflowing hot gases from and shielding a variable portion of the superheater against the effect of the hot gases.

This will generally involve housing the superheater in a compartment or cavity which is substantially wider than the superheater as measured across the general direction of flow of the hot gases so that there is therein a space unoccupied by the superheat-er into which the hot gases can be forced by the cooled gases so that the hot gases pass onward out of contact with at least a part of the superheater. The recirculated cooled gases can be made to enter the superheater chamber for this purpose through one or more nozzles fed by a fan. The variation of the superheat temperature can be eifected by varying the rate of discharge of the fan, or by cutting nozzles in and out at appropriate times, or by altering the direction of discharge of the cooled gases from the nozzles.

An example of a boiler in accordance with the invention will now be described with reference to the accompanying drawing which is a diagrammatic sectional elevation of the boiler.

The boiler shown in the drawing is a D-type boiler of a well-known type having an upper steam and water drum and a lower 'Wa-ter drum 12 connected by banks of steam generating tubes 14. It is fired by burners 16 in a furnace 18, the combustion gases following the path indicated by the full-line arrows through the steam generating banks 14 and an economiser 19 to an outlet 20 leading to a flue.

On the furnace side of the steam generating bank 14, there is a superheater 22 taking steam from the drum 10. The superheater is arranged in a compartment or cavity bounded by baffle walls 24 and 26 so that there is an ample unoccupied space 28 on the furnace side of the superhe'ater.

Between the superheater 22 and the bafiie wall 24, there are two pipes 30' extending across the furnace and provided with nozzles 32. positioned at intervals across the furnace. The nozzles are connected to the outlet of a 3,098,469 Patented July 23, 1963 "ice fan 34 arranged to take cooled combustion gases from the space 36 between the economiser 19 and the flue.

When the fan 34 is put into operation, cooled gases are delivered as shown by the broken line arrows through the nozzles 32 with the result that the hot gases from the furnace are diverted towards the baliie wall 26. The extent to which they are so diverted depends on the orientation of the nozzles and the rate at Which the cooled gases emerge from them. By varying one or the other of these factors, the heat put into the steam in the superheater can be varied. It will be appreciated that a considerable variation of the final steam temperature can thus be effected as diversion of the hot gases away from the superheater is accompanied by subjection of a part of the superheater tothe action of the cooled gases.

The fan can be controlled manually or automatically by, for example, a controller which responds to changes in the steam temperature at the outlet of the superheater.

Alternatively, or in addition, provision can be made for cutting in and out one or more of the nozzles or for varying their orientation. This however, is not the preferred method of operation as it involves the provision of mechanical parts in a hot area of the installation.

What is claimed is:

A water tube vapor generator comprising an elongated bank of superheater tubes; means housing said bank and defining an elongated gas passage which extends longitudinally of said bank, said bank of superheater tubes and housing means being in a convection zone of said vapor generator, gas inlet and outlet means adjacent the ends of said passage such that the flow of hot gas is approximately in the direction of the length of the passage and along the length of said bank of said superheater tubes, said passage being substantially wider than the bank as measured across the general direction of flow of the gas and said bank being disposed along one side of the passage so as to provide on the opposite side a space approximately coextensive with the bank which is unoccupied; said gas inlet means, passage and bank however being arranged such that the flow of hot gas normally is through the superheater; means for withdrawing cool gas from an area of said generator downstream of said space; and adjustable means disposed in said passage along a side of said bank removed from said space adapted to blow said cool gases in a substantially transverse direction across said bank in a manner to divert a variable propor tion of the stream of inflowing hot gases into said space.

References Cited in the file of this patent UNITED STATES PATENTS 2,695,599 Amnacost Nov. 30*, 1954 2,798,464 Seidl July 9, 1957 2,922,406 Zoller Ian. 26, 1960 FOREIGN PATENTS 373,860 Great Britain June 2, 1932 143,725 Sweden Jan. 19, 1954 

